Slide-rule.



Patented Jan. 5, 1915.

2 SHEETS-SHEET l.

P. C. FARMAR.

SLIDE RULE.

APPLICATION FILED MAY26.1913.

. PARMAR SLIDE RULE. APPLICATION FILED MAY 26,1913.

FRANK CHARLES FARMAR, OF WATERLOO, NEAR LIVERPOOL, ENGLAND.

SLIDE-RULE.

Specicaton of Letters Iatent.

Patented Jan. 5, i915.`

Application led May 26, 1913. Serial N o. 769,793. l

MAR, a subject of the King of England, re-A siding at 2 Neville road, Waterloo, near Liverpool, in the county of Lancaster, Eng land, have invented certain new and useful improvement-s in or Relating to Slide-Rules, of which the following is a specification.

This invention relates to fiat slide rules, and has for its object to provide a rule for commercial calculations, which, for a given size, shall have large calculating capacity, and which may be easily read.

A slide rule, according to my invention, essentially comprises a fiat slide and a revoluble roller (or rollers) tube, cylinder, `or the like, fitted or mounted in the rule, and arranged to operate with said fiat slide, on one of which, preferably the roller, are arranged a plurality of logarithmic graduations of money expressions, and on the other of which are arranged logarithmic gradua-l tions of discount, profit on turnover, or profit on cost, or any two or all of such graduations. Particular features orlcnaracteristics are hereinafter desbtibed and pointed out in the claiming clauses concluding this specification.

In the accompanying sheet of explanatory drawings there is illustrated a rule according to this invention.

Figure l is a front view, Fig. 2 an end elevation, and Fig. 3 a rear view,of the rule. Fig. 4 shows the complete expressions which appear around the circumference of the roller or cylinder.

a represents a frame rod, or bar, the respective ends whereof are firmly secured to and between the respective pairs of sheet metal end clamps b. c indicates a slide which is positioned between said rod a and two wooden or like filling pieces or blocks l disposed and secured between clamps b on the principle ,of the tongue and groovesee Fig. 2. ,-f

e designates a tube or cylinder constructed of transparent celluloid, within each end whereof is fitted a closing` piece or plug f of wood, cork, metal, or other suitable material, provided with a pin g which is adapted to revolubly tit in a socket provided for it Within the adjacent filling piece or block UZ; alternatively, a metal rod may be passed through said tube or cylinder e and through apertures provided in the closing or filling pieces or blocks d, so that the protruding ends, by projecting into sockets provided in the rule frame, form pivots for roller e. or pivot pins may project from the ends of the rule frame into sockets in said filling pieces The end or edge of slide c which is adjacent to said roller e is grooved or recessed somewhat (Fig. 2) for the purpose of accommodating the latter. The logarithmic graduations of money expressions are printed preferably from a copper plate on a sheet zjof paper, and this after being suitably bent or mounted around a thin cardboard tube is fitted within said transparent celluloid cylinder e, so that `the expressions or graduations may be viewed. from the outside thereof: the ends of said sheet it are firmly held by a friction t between the inner wall of cylinder e and the closing or end pieces or plugs f (see Fig. l) thus said cylinder and sheet will revolve as one, the sheet being thoroughly protected by the Celluloid raising. Alternatively, said sheet may be mounted around a hollow or solid roller of wood, or other suitable material, and varnished or otherwise treated to render it washable; or the graduations and figures may be engraved or inscribed on a roller of wood or other suitable material. ln order, however, to provide an accurato rule at a low cost of production, I prefer to employ said tube or cylinder of transparent celluloid and a printed paper litted within same. On the roller, which is rotated by the linger and thumb of the user, are arranged logarithmic graduations of money expressions extending from and to any desired amount and in' any system of coinage. As illustrated in Fig. i the expressions range from 1 cent to 300 dollars arranged in parallel lines in the following order 1 cent to 5 cents; 2 cents to l0 cents; 5 cents to cents; lO cents to 50 cents; cents to l dollar Q5 cents', 50 cents to dollars 5() cents; l dollar to 5 dollars; '2 dollars to l() dollars; 3 dollars to 25 dollars; l0 dollars to dollars; 25 dollars to 125 dollars; (30

dollars to 300 dollars. On slide c which cooperates with said cylinder e are arranged divisions indicating discount, profit on turnover, and profit on cost, respectively: these dir visions cover a range extending preferablyas illustratedfrom discount to 66% profit on turnover and 200% rofit on cost; they may be printed or inscribed on paper, Celluloid, or other suitable material which is secured to the slide, or may be engraved or inscribed on the material thereof.

As a modification, the scales may be reversed, the money expressions appearing on the slide and the profit and discount graduations on the roller. v

On the reverse side of the rule are two scales marked A` and B respectively on frame a and slide ofthese scales facilitate calculations beyond the limits of roller e.' these may also be used for general calculating purposes when desired.

if found necessary or desirable, I may employ a pawl and ratchet arrangement in connection with the roller e for the purpose of'positively maintaining it in any one position until wilfully moved therefrom. Further, an end of said roller e may protrude beyond the rule frame a and a wheelhandlc or finger and thumb piece be fitted thereon. Or, if the rule be constructed of wood, the ends may be reduced and fitted in a revoluble manner within metal end clamps.

may employ twfe or more revoluble rollers on a single rule, with the object of increasing the calculating capacity thereof.

Examples of the uses of a rule scaled as illustrated 'in the drawing anneed hereto.

An article costs -i dollars. Vhat must be the sellinfr )rice to fain 20% on the turn- 23 b l over? Answer dollars.

3. An article sells at 5 dollars. YVhat must be the buying price to gain 20% on the turnover'.Z Answer 4 dollars.

N. 3.111 the first two examples Par on slide has beeny set to the cost price on roller; then the selling price and percentage profit simultaneously appear. In the third case the percentage profit has been set to the selling price and the roller looked at over i Par for thebuying price.

Discount-Set Par on slide to 5 dollars on roller. The rule as now set answers simultaneously each of the following questions, viz

1. An article is bought (or sold) at 5 dollars, less 5% discount. lVhat is the net buying (or selling) price?.l Answer e dollars cents.

2. An article is sold nominally at 5 dollars, but actually at 4 dollars 75 cents. iVhat rate of discount is that? Answer 5%.

3. iVhat is 5% ofi 5 dollars? Answer 25 cents (viz. the difference between 4 dollars 75 cents and 5 dollars).

N. B.-In all of the three foregoing examples Par has been set to the 'buying or selling price; and the net price and rate of discount simultaneously appear. A

Proji'z and discount combined-Set 5% discount on slide to 6 dollars on roller. The rule'as now set answers simultaneously each of the three following questions viz:-

(1). An article costs 6 dollars. At what price must this be sold in order that 5% discount may be allowed off the selling price and 20% profit made on the turnover? Answer 7 dollars 90 cents I (2). An article costs G dollars and is sold for 7 dollars 00 cents less 5% discount. What is the net percentage profit on the turnover? Answer 20%.

(3). An article sells at 7 dollars 90 cents less' 5% discount. lhatinust it be bought for in order to realize 20% net profit on the turnover? Answer G dollars. N. B.ln the first two cases the rate of discount has been set to the cost price; then the gross selling price and net percentage prolit simultaneously appear. In the third example the required net percentage profit has been set to the gross selling price, and the roller looked over at the rate of discount for the buying price.

A cursor may be used-if necesary-with the rule to facilitate reading.

Having now described my invention what Let.

I claim as new and desire to secure by ters Patent is 4 n a slide rule, an. oblong frame constituting a handle, said frame having the upper edges thereof provided with' a tongue extending vtrom one end of said frame t0 the other, a set of parallel clamps carried by the sides of said -frames at each end thereof and extending at yright angles to the tongue edge of said lframe, blocks mounted 'be tween the clamps of each set and having tongues at the lower edges thereof confronting the tongue of said frame, said blocksj having sockets in the confronting faces thereof, a cylinder between said blocksjin parallelism with said frame and having pins at the ends thereof extending into the sor-kets of said blocks for revolubb7 supporting said cylinder, and a slide movable lengthwise between said trarne and said cylinder 'and hailing .the upper and lower edges In testimony whereof I affix my signature thereof provlded with grooves extending in presence of two Witnesses. throughout the length of said slide, one of which normally'receives the tongue of smid FRANK CHARLES FARMAR' 5 frame, and the other groove adapted to fitnessesz receive the tongue of one of said blocks JOHN H. VALKER,

when shifted in either direction.- H. VLLLIAMS. 

